This invention relates to the field of intravascular catheters, and more particularly to a dilatation catheter for percutaneous transluminal coronary angioplasty (PTCA).
In PTCA procedures a guiding catheter having a preformed distal tip is usually percutaneously introduced into the patient's femoral artery by means of a conventional Seldinger technique and retrogradely advanced therein until the distal portion of the guiding catheter is located within the patient's ascending aorta with distal tip of the guiding catheter seated in the ostium of a desired coronary artery. The proximal end of the guiding catheter is torqued from outside the patient to guide distal tip of the guiding catheter into the desired ostium. A guidewire is positioned within an inner lumen of an dilatation catheter and then both are advanced through the guiding catheter to its distal end. The guidewire is first advanced out of the distal end of the guiding catheter into the patient's coronary artery until the distal end of the guidewire crosses a lesion to be dilated. Then the dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient's coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 4 atmospheres) to expand the arterial passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
Commercially available over-the-wire dilatation catheters for angioplasty and other vascular procedures usually comprise an elongated shaft with an inflatable dilatation member on a distal portion of the shaft and an adapter on the proximal end of the shaft for the delivery of inflation fluid through an inner lumen extending through the catheter shaft to the interior of the inflatable dilatation member.
The progression of improvements in dilatation catheters generally has been to make the catheters with lower profiles and with the proximal portions of the catheters being much stiffer than the distal portions. However, this progression has also increased the difficulty in forming smooth transitions between the various sections of the catheter shaft. This is particularly noticeable with catheters having proximal portions formed of metallic tubing such as stainless steel hypotubing.
What has been needed is a dilatation catheter which has a stiff proximal portion for pushability, a very flexible distal portion to facilitate advancement over a guidewire, i.e. trackability, within a patient's coronary anatomy and a smooth transition between the proximal and distal portions. The dilatation catheter of the present invention provides such a combination of such desirably properties.